COLOR  SENSITIVENESS  OF  PHOTO-ELECTRIC  CELLS 


BY 

WILLIAM  PARKERSON 

B.A.  Tulane  University,  1919 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  MASTER  OF  SCIENCE  IN  PHYSICS 
IN  THE  GRADUATE  SCHOOL  OF  THE  UNIVERSITY 
OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


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UNIVERSITY  OF  ILLINOIS 
THE  GRADUATE  SCHOOL 

J's-ins -192-^- 

I HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 

SUPERVISION  BY WILIT.;.: ' PAn!<I^^S.QN 

F.N'riTT.F.D  COLOR  EEVETTIV^TI-'t^-P?  ^7  - U-IC  OFLIxU 


BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF LAST^R  QF  SCIEH-CE — 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


Required  for  doctor’s  degree  but  not  for  master’s 


Digitized  by  the  Internet  Archive 

in  2015 


https://archive.org/details/colorsensitiveneOOpark 


TABLE  OF  C05JTENTS 

I  INTRODUCTION ' . . . 

Simple  Cell,  B’ig.  la 

II  APPARATUS  AND  i\IANIPULATION  .... 

Optical  System,  Fig. lb  

Arbitrary  Scale,  Fig.  3 

Diagram  of  Connections,  Fig.b.  . 

Ill  CALCULATIONS  AND  RFSULTS  

Data  on  cell  KH  No.  1 

Data  on  cell  KH  No.  2 

IV  CONCLUSION  


1 

1 

3 / 
. b 

4 

5 

6 
8 
9 

10 


T.  INTR0DUCTI05 

Tns  hi>^tc:-cy  cf  the  phot ect ric  srfect  ,"it^ 

discovery  by  Eertz,  in  1887  that  a"  arc  could  ''-e  strucV"  --‘t  -d'-i.  o 

terminals  at  a lower  vcltage  when  a neio hbcr irp  arc  was  ruuy.iih.-., 
than  -Alien  the  latter  was  shut  off.  In  the  follohin^  year  Hallwaons 
found  that  a "stallic  pldtc,  nes’atively  char;yedj  lost  tnat  chr.rp© 
wnen  exposed  to  ultra-violet  li^ht.  7ince  these  two  pioneer  dis- 
coveries , tne  phenomenon  of  phot  ■^-electricity  has  been  studied  oy 
many  invest igatcrSj  frcai  bctn  a theoretical  and  a utilitarian  point 
of  vie'...  In  this  connection  may  be  menticr-ed  such  - er  as  Lao-enour;^' j 
rister  and  Geitsl,  Lenard,  Pchl  and  ^rinpsheim,  aoid  Buphes. 

Finally^  a phot oel^-ctr ic  cell  hc^s  oeen  devaloped,  whichj  iu 
its  sii.  olest  f CT;.. j IS  sii' A'jii  o ;itical''-y  iii  Fip«ln.  !■-  ccnsi3.>si 


r P - 

O-  WV  gj 


Fig.  la 

^lass  tube,  clC'^ed  at  both  ends,  h:,vin_  a sp-i.  et: oai  :ulb  at 
the  center.  ?>-^  a-ol  of  this  bnld  is  silvered,  sc  that,  while  sorv- 
ing  as  negative  terminal,  it  also  operates  to  focus  the  i^oioent 
lipht  on  ? is  the  positive  terminal,  consist i;:a  cf  a wire  led  ir 
tiu'cuph  oiae  end  cf  the  cell  ahv*  G ent  in  the  for-.-  of  a cii'Oi e,  -tcr^.-os 
which  t'.vc  f iiier  ,vir-es  c-.,re  strun;-;  aiam;- c-cicaij-y . T;..aoe  or  .Sj  -.''ires 
arid  the  circle  aoout  the-i:.  are  covered  .vith  a thin  lay.-r  ot  .--n  al  u.li 
rmetal  and  the  cell  is  sensitized  by  hydro^^en.  A detailed  dascrip- 
tich  of  the  ouha t r Lf ct  1 vjv.  ana  p- rea-.- Lot  io.-  cf  su-on.  je-j-xS  ,,,c-.y 


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in  the  Physical  Review,  Vol.7,  p 62,  1916. 

If  a potential  difference  be  placed  across  tne  terminals  of 
the  cell  when  no  light  is  incident  upon  it,  no  current  will  flowj 
that  is  to  say,  the  cell  shows  no  ’’dark  current”.  On  the  other  han 
if  light  impinges  upcn  a cell,  which  has  a difference  of  potential 
between  its  terminals,  a current  will  flow.  If  we  consider  the 
coulombs  of  electricity  which  flow  through  the  cell  per  erg  of  in- 


cident light  energy  (the  specific  photc-electric  sensitiveness), 
this  factor  will  be  found  to  change  very  appreciably  with  the  wave 
length  of  the  incident  light.  The  color-sensitiveness  curve  for 
the  alkali  metals,  unlike  that  for  other  metals,  possesses  a reso- 


nance peak  in  the  violet  end  of  the  visible  spectrum.  The  wave 
length  at  which  the  maximum  of  this  peak  occurs  shall  be  denoted  by 
^max*  Obviously,  in  any  investigation,  in  which  a photo-electric 
cell  is  to  be  used  as  a iteasuring  instrument,  a thorough  knowledge 
of  the  characteristics  of  the  cell  is  essential.  Accordingly,  cells 
prepared  in  this  laboratory  by  Dr.  Kunz,  to  be  used  by  Dr.  Shelford 
in  certain  experiments,  were  turned  over  to  the  writer  for  cali- 
bration. The  problem,  then,  was  to  collect  the  necessary  data  and, 
with  this  data,  to  plot  the  color-sensitiveness  curve  for  each  of 
these  cells. 


It  should  be  clearly  understood  at  the  cutset,  that  no  very 
high  degree  of  accuracy  is  claimed  for  the  measurements  of  the  spe- 
cific photo-electric  sensitiveness.  The  form  of  the  curve  and  the 
value  of  more  important  than  the  absolute  values  of  the 

specific  photo-electric  sensitiveness. 


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5 


II.  ANr  MAI'IIPULATIO:/ 

Tne  spectruai  used  in  the  /..i^asure.^  ent 3,  .vas  oou^lnsd 

optical  syster;.^  shc/m  dia^ro...:.r/.at  ically  in  Fi'_.lo.  F is  a 


larr.p  which  fnrniened  a line  source,  nii^n  candle  power.  Tp 
and  Dj  are  diaphra^Tos  used  to  elifi:inats,  as  'r--.r  as  possible,  stray 
light.  Lp  and  Lg  focused  the  light  fro.r  F_  at  the  slit.  ^ served 
to  render  the  light  parallel,  and  _L^  tc  define  the  spectrum. 

Ic  was  necessary  tc  icnc”'  the  energy  distribution  in  tae 
spectrurr.  and  also  the  wave  length  at  every  point  in  it.  To  effect 
these  calio  1'o.t ions  an  arbitrary  scale  he.d  to  be  cnO'Sen  alcrn  tne 
spectrun..  This  arbitrary  scale  Sy  togeoher  with  the  attacned  slit 
and  table  L and  T,  respectively,  is  shc-em  dia.wra:id.ctically  in  Fig.  3. 
This  arrangement  was  placed  just  beyond  (Fig.  lb''  in  such  a posi- 
tion txiat  the  lengtn  iirection  of  the  slit  L (Fig.  2^  was  perpen- 
dicular to  tne  plane  of  the  paper  (Fig.  lb)  and  so  tnat  by  tu.rning  R 
(Fig. 3),  L (Fig. 2)  could  be  sniftea  bach  and  forta  in  a direction 
perpendicular  to  tne  principal  axis  of  (Fig.  lb''. 

A Hilger  constant-deviat ion  spectrometer  ".as  calibrated 
with  a Helium  Pliioker  tube.  This  sp.jvjorc„:et or  was  then  used  to 
measure  the  wave  length  ct  the  light  passing  throu^^h  L (Fig.  3}  for 
l<i  points  on  tne  arbitrary  scale  S (Fi.g.3).  These  points  -tere  so 


cncssn  that  the  wavs  lermth  ranoad  frcr/,  400  uu  '^o  -600 


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6 

III.  CALCULATIOIMS  AND  RESULTS 

ift 

Tiiermo-pl,le  Calibration.-  According  to  F.  Coblentz  the 

radiant  energy  at  a distance  of  one  meter  from  a Hefner  lan;p  is 

26.0-10“^  g.  cal.  per  sq.cm,  per  sec.  when  no  diaphragmi  is  used. 

Taking  Joule's  equivalent  as  4.16?  • lo"^  ergs  per  cal.,  this  value 

becomes  1089  ergs  per  sq.cmj.  per  sec.  at  one  m'eter  distance.  The 

thermo-pile  was  placed  75  cm.  fromi  the  lamp  and  for  this  distance 

the  energy  per  sq.cm,  per  sec.  is 

100. 

1089(7^)2  = 193?  ergs. 

The  average  deflection  of  the  galvanorj. at er  was  63.41  mm.  Hence,  a 
deflection  of  1 mm.  of  the  galvanometer  corresponded  to  a flow  of 
energy  of 

1937 

q2""ai  - 31.04  ergs  per  sq.cm,  per  sec. 

Scale-wave-length  Calibration. - The  light  passing  through 
L (Fig.  3)  was,  of  course,  not  exactly  monochromatic.  Consequently, 
for  every  setting  of  the  scale  S (Fig. 2),  readings  of  the  extreme 
wavs  lengths  were  taken  ana  tne  average  of  these  two  extremes  was 
used  as  the  mve  length  for  that  position. 

Scale-energy  Calibration.-  The  area  of  the  slit  L (Fig, 3) 
was  .2843  sq.cm.  Therefore,  the  energy  passing  that  slit  for  1 mm. 
of  deflection  of  the  galvanometer  was 

31.04  • .2842  = 8.826  ergs  per  sec. 

The  Photo-electric  Current.-  The  galvanometer  used  to 
measure  the  photo- electric  current  had  a sensitiveness  of  2711  meg- 
ohms. Its  figure  of  merit  was  therefore 

37ltlO"S  = 2'®®®  ■ 


* Bulletin  of  Bureau  of  Standards. Voi.li,j3.g9,  1914 


V 


I 


(I 


il 


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' - ' 

i • A , , , i 


Since  the  scale  vvas  1.765  meters  from  tne  mirror ^ 1 mm.  deflection 

indicated  a current  of 

5.88S  • 10"^*^  o i^-lO 

“ 3.0899  • 10  amperes. 

The  data  taken  for  the  potassium  hydride  cells  numbers  1 anc 
2,  are  shown  below  in  tabulated  form. 

Column  No.  1 gives  the  scale  readings. 

Column  Wo.  2 gives  deflection  of  thermopile  galvanometer  in 
miiiimet  ers. 

Column  Wo.  3 gives  energy  in  ergs  per  second. 

Column  No. 4 gives  deflection  of  photoelectric  galvanometer 
in  millimeters. 

Column  No. 5 gives  photo-electric  current  in  amperes  x 10“^^. 

Column  No. S gives  specific  photo-electric  sensitiveness  in 
coulombs  per  erg  x 

Column  No.  7 gives  wave  length  inyuyui  . 


s 


Table 

I 

Cell  ZE 

No.  1 

Voltage  on 

Cell  = 

= 95.  2 

1 

2 

3 

4 

5 

6 

7 

412 

2,  0 

17.653 

6 . 5 

13. 584 

. 7693 

413.  5 

415 

2.  1 

18. 535 

9.0 

18.809 

1,0150 

413.6 

420 

2.4 

21. 182 

16.0 

33, 438 

1,5790 

418,6 

425 

3.8 

33.539 

29.3 

61.234 

1. 8260 

425. 1 

430 

6.1 

53. 339 

51,3 

107.212 

1.9900 

432.  0 

435 

9.4 

82.964 

89.2 

186. 419 

2.2470 

439.  5 

440 

14.9 

131. 507 

153.  0 

319. 755 

3.4300  ' 

CO 

o 

445 

24.9 

219. 767 

233.  3 

485.484 

2.2100 

459.8 

450 

39.5 

346.627 

378.0 

580. 992 

1.5666 

473.9 

455 

62.  5 

551.625 

274.  0 

572.833 

1.0380 

490.5 

460 

99.  5 

878. 187 

220.  0 

459. 778 

0.5333 

509.5 

465 

160.2 

1413.925 

134.8 

281.718 

0.19S2 

536.6 

470 

247.5 

2184.435 

59.2 

123.722 

0;  0663 

571.0 

475 

355.  0 

3133.230 

20.4 

42. 634 

0.013S 

617. 6 

Elcc^yic  Scpsihii'e^css. 


9 


T^ol  s 


Csll 

TCH 

Voltage 

on  C 

1 

3 

4 

413 

3.0 

17.653 

3. 

415 

3.1 

15.535 

5. 

430 

2.4 

31, 182 

8. 

425 

3.8 

33. 553 

15. 

430 

6.1 

53 . 833 

26. 

435 

C' t 4 

S3. 334 

48. 

440 

14.3 

131.507 

85. 

445 

24.3 

219. 737 

148. 

450 

39. 5 

348. S37 

319. 

455 

62.5 

551.625 

268. 

430 

^ SI 

. 0 

878. 187 

252. 

435 

160.2 

1413.925 

230. 

470 

247.5 

2184.435 

114. 

475 

« 0 

3133. 230 

34. 

= 130.5 


5 

6 

7 

7.942 

0. 4438 

413.5 

10.867 

0.5860 

413.6 

17.555 

0.3350 

418.6 

33. 393 

0.9650 

425 . 1 

54. 337 

1.0080 

433.0 

100. 315 

1.2090 

439.5 

179. 104 

1.3610 

44910 

309. 3b5 

1.4070 

453.8 

457. 68S 

1. 3140 

473.9 

531. 138 

1.0170  ■ 

490.5 

539.351 

0.6710 

509.5 

461. 450 

0.3253 

533 . 3 

359 . 293 

0.1096 

571.0 

71.057 

0.0227 

S17.6 

II 

Wc 

ell 

6 

3 

4 

5 

0 

0 

7 

0 

0 

5 

0 

8 

5 

0 


10 

From  the  values  found  in  the  last  two  columns  of  the  data 
for  each  cell,  the  corresponding  color-sensitiveness  curve  is  ob- 
tained. It  may  be  seen  frcir  the  curves  that,  for  KH  No.l,  = 

493yyx  , and  for  I\H  No.  3,  ~ ^cSSyxyu., 

IV,  CONCLUSION 

The  work  had  to  be  done  with  extreme  cars  and  at  a time 
when  the  atmosphere  was  cool  and  dry,  to  prevent  leakage  effects. 
All  the  diagrams  contained  herein,  with  the  exception  of  No. la, 
have,  by  the  kind  permission  of  Miss  F.F.  Seiler,  been  taken  from 
her  doctor’s  thesis. 

I take  this  occasicn  tc  express  appreciation  to  Profes- 
sor E.  H.  Williams  and  Professor  Jakob  Kunz  for  the  interest  taken 
in  my  work  and  to  thank  Professor  A.P.  CarK.an  for  the  use  of  the 
lu'c oratory  facilities. 


